The Republican presidential race has taken on a white-hot intensity here as Minnesotans prepare to caucus Tuesday night, with major candidates scurrying across the state hoping to gain an edge that could reshape the contest.

The caucuses come at a critical point, with several of the candidates jockeying for survival, hoping to once again unseat current frontrunner Mitt Romney.

At a last-minute rally in the Minneapolis Convention Center, more than 1,800 people jammed in to hear Ron Paul. "They call us dangerous," he told the cheering crowd. "We are dangerous to the status quo and to the people who have been ripping us off!"

Earlier in the day, Paul drew more than 900 supporters in St. Cloud.

Rick Santorum kicked off his day in Rochester, telling an overflow crowd at the Kahler Hotel that frontrunner Romney was not only "unqualified" to debate President Obama on health care, but should be "disqualified."

Romney returned fire via a surrogate, former Gov. Tim Pawlenty, and in scorching local mailers that savaged Santorum's congressional record in Washington.

Newt Gingrich issued a blistering attack on President Obama, vowing major and immediate change, in his first pre-caucus appearance in Minnesota Monday night.

In a speech to several hundred supporters at the Ramada Hotel in Bloomington, Gingrich was unruffled by hecklers and focused his attack on Obama. He also aimed some shots at Romney, whom he accused of being a moderate who would not undertake the needed changes in Washington.

"The real underlying question in this campaign is whether we want an election that involves real change on a large scale,'' Gingrich told a packed conference room. "Or whether we want an election that has small differences, fighting over who is going to manage the decay.''

GOP horse race

The fiery rhetoric comes as the campaigns take aim in the impossible-to-call Minnesota caucuses.

Dave Nesberg of Rochester grabbed a yard sign on Monday, ready to get more involved in this GOP primary horse race, he said, than he ever has been before.

"I'm not really into politics," he said. "This is very unusual for me. This is the first time I've ever made the effort. The first time in my life."

For the past few years, he said, he's gotten more concerned about government policies, and Santorum's message that power should come from the bottom up, and not the top down, resonated with him.

But political watchers of late are zeroing in increasingly on Paul, who trails in recent polls but who has spent months quietly building a formidable army of supporters that may wield an outsized influence in Tuesday's non-binding poll.

A wide spectrum of Republican strategists now say Paul's passionate and deeply devoted followers could swarm the caucuses, giving the Texas congressman his first win and potentially creating a seismic reshuffling of the GOP field.

National political experts are paying particularly close attention, because the state has a history of embracing quirky politicians, potentially giving Paul his last, best shot.

With Romney piling up impressive wins in New Hampshire, Florida and Nevada, time is running out for an alternative candidate to emerge as a credible threat. Minnesota has become the logical place to take a stand, make headlines and shake up the race.

'You have to do well'

Santorum, who will be campaigning in Blaine on Tuesday, has hit spots from Bemidji to Waconia urging voters to hit "reset" on the race.

"If you're vying for that contender spot, you have to do well this week," said Gary Borgendale, a conservative Christian activist who is helping Santorum in Minnesota. Borgendale was among a fistful of endorsements Santorum released Monday night that included a dozen state senators.

Polls have found Minnesota's caucus nearly impossible to predict.

Only a sliver of GOP voters will turn out for the straw poll, perhaps as few as 60,000. A week ago, one poll showed Gingrich leading. On Sunday, the same polling outfit had Santorum holding a slight lead, with Romney in second, then Gingrich and Paul trailing.

The attention is unusual because Minnesota's caucuses are nonbinding. But in a race this contentious, even bragging rights count.

"Very few people in that next state are going to know how meaningless a caucus is or what it has in terms of bearing in the long term," said national GOP strategist Chris Ingram, who supports Romney.

Pawlenty on Monday filled in for Romney, speaking before a gathering of about two dozen. He challenged Santorum's conservative credentials and accused him of being addicted to government largesse.

In the closing hours before the caucuses, Minnesotans were far from converging on a single candidate.

Jennifer Maki, 24, drove down from Duluth to hear Paul. "He's the only one who will speak the truth about the economy and make the actual real changes that other politicians area afraid to make," she said.

Melanie Stoen, of Austin, showed up to the Santorum event with her seven children in tow.

"I've heard so many people say, 'I like Rick, but I'm not going to vote for him because I don't think he has a chance,'" Stoen said. "Of course he doesn't have a chance if we don't support him! ... I'm going to the caucus tomorrow for the first time in my life, and I'm bringing my kids."

Carolyn Christensen of Minneapolis and Shirley Overlin of Bloomington turned out to hear Gingrich, whom they believe is the strongest GOP candidate to put up against Obama.

"He has the positive ideas about where to take the country,'' said Christensen. "He's pro-life, always has been, and he's for smaller government.''